1. Field of the Invention
This invention pertains generally to can processing machines, and more particularly to a novel can extractor for use in rotary cookers and coolers in the canning and food processing industry.
2. Description of Related Art
A can extractor is an apparatus that removes cylindrical cans of food product from rotary cookers and coolers typically used in the food processing industry. In this example, a rotary cooker/cooler is a horizontal cylindrical shell with a rotating cylindrical reel of parallel angle bars that push cans of food product along a spiral guide or thread mounted on the inside wall of the shell. In an atmospheric rotary cooker, hot or boiling fluid is used to cook or sterilize the food product in the can.
In a typical configuration, a star wheel and a clover wheel or a pair of parallel rotating star wheels between circular flanges are positioned at the extraction end of the shell and are synchronized to mesh with the angle bars of the reel to engage the can in the recess between two star points of the star wheels and move the can from a cooker to a cooler or from the cooler to a discharge chute.
In another configuration, a lobed gear wheel is positioned at the extraction end of the cooker/cooler and beneath the rotating reel. A can is pushed out of the reel by a lobe of the gear wheel poking between the angle bars of the reel and pushing the can through an opening in the cooker to a pocket valve or chute.
Many existing rotary cookers/coolers have been in service for decades. A mild steel is typically used for can handling components such as the flanges, and star wheels because mild steel parts are easy to fabricate at a reasonable cost. The extractors on these cookers are in continuous use during the canning season and subject to heavy use, excessive wear and are exposed to a wet, corrosive environment associated with food cookers. As a result, rust forms on the mild steel components at wear and contact surfaces. The rusty surfaces of the extractor transfer rust to the exterior of the cans during extraction causing damage, discoloration and potential contamination to the product resulting in rejection of product and revenue loss. It is not uncommon for food processors to replace most or all of the mild steel components of an extractor after each canning cycle due to wear and corrosion.
Another source of product loss associated with existing can extractors is scratching cans while in the extractor. Wear and corrosion on the mild steel star wheels and flanges develop into sharp edges and rough surfaces. As a can is moved from the reel to the extractor or from the extractor to a discharge chute, the can will rotate and contact these sharp edges and rough surfaces which can scratch the rotating can. A scratched can is typically rejected because it is cosmetically unmarketable or the location of the scratch can potentially contaminate the product. A tin alloy steel is typically used for food cans to resist scratches from the extractors. If scratching were minimized or eliminated in a particular food processing system, a tin-free steel (TFS) could be used at a great cost savings.
A further source of product loss is a can jammed in an extractor. Jams can result from failed parts, defective or bulging cans or misalignment of parts due to vibration or wear. If the jam is not quickly resolved, all the product remaining in the cooker can be ruined. If repetitive extractor jams cause significant delays in food processing, harvested food product can perish before it is canned and cooked.
Existing extractors are typically configured with a rotating sleeve of soft metal, such as brass, configured to rotate directly on a shaft. Keyways or set screws are used to couple the hubs of the flanges and star wheels onto the rotating sleeve. These couplings are not designed to give or slip. When a jam occurs, the torque transmitted through the keyways or set screws of the hubs can damage or distort the soft metal sleeve requiring immediate disassembly and replacement. Torque from a jam can also damage hubs or shafts requiring costly downtime and replacement. Further, the rotating sleeve must receive periodic lubrication or seizing can occur.
What is needed is a can extractor for a rotary cooker/cooler that does not scratch or transfer rust to the cans. Additionally, a can extractor that is easy to maintain, is not prone to jamming, and does not require significant downtime to clear a jam is desired.